Surgery for stress urinary incontinence (SUI) by mid-urethral sling (MUS) has become a standard widely used in routine clinical practice. The retropubic procedure is the one for which there is the most long-term data. Transobturator route (out-in or in-out) has been developed with the intention of simplifying the surgical procedure and reducing the risk of complications. 
In the 2010’s, growing awareness was raised of serious complications of surgical meshes used in urogynecological surgery.
Unlike clinical trials, the registries offer the possibility of specifying the occurrence of rare events in routine clinical practice.
Our objective is to specify the incidence and to describe the serious complications related to surgery by MUS in routine clinical practice according to the type of sling (retropubic or transobturator) using the long-term data from the  French VIGI-MESH registry(1). We also aimed to compare the reccurence rate of both approach.

All patients who benefit of the MUS by retropubic or transobturator route since February 2017 were included in the analysis. 
We collected all serious complications (Grade III and Grade IV according to modified Clavien-Dindo classification) and reoperation for recurrence of SUI. 
Intra-operative injuries requiring cancelled placement of the sling were counted as grade III. Declared complications were analysed to assess imputability of the MUS procedure. In accordance with the design of the registry, the surgeons reported complications and reoperations on a specific form during follow-up. To ensure the completeness of the surgeons’s reports (for complications and reoperations), we checked the data collected by each hospital’s data department to link and monitor medical events after the index surgery. Annual follow-up questionnaires were also sent to seek for new unknow complications. The end of the study period was October 2021.
To balance the baseline differences between both groups, we used a propensity score approach with inverse probability of treatment weighting with pre-specified variables (age, body mass index, smoking, diabetes, previous hysterectomy, previous surgery for SUI or pelvic organ prolapse, physical status score and menopausal status).
Two Cox proportional hazard’s models with a frailty term taking into account the centre effect and the occcurence of concomitant hysterectomy or prolapse surgery were used to compare both approach.

Between February 2017 and October 2021, 3316 women underwent surgery for SUI among which 2683 benefited of MUS by retropubic (1831 women) or transobturator (852 women) route: 211 out-in and 639 in-out (2 unkown).
Women in the transobturator group were older than the others (58.8 years vs 56.9 years, p<0.001) and history of SUI surgery was more frequent in the retropubic group (13.1% vs 3.2%, p<0,001). 
The maximum follow- time was 88 months. We observed serious complications for 124 women: 100 patients in the retropubic group and 24 in the transobturator group.

 25 complications occurred in the retropubic group during surgery or within the first 48 hours following surgery: 8 grade III intraoperative injuries (4 bladder wounds, 3 urethral wounds and 1 vascular injury), 1 intraoperative hemorrhage, 13 obstructed micturitions, 2 postoperative hematomas and 1 neuropathic pain on the obturator territory. 
In the transobturator group, 5 complications were reported during surgery or within the first 48hours: 3 grade III intraoperative injuries (2 vaginal and 1 urethral wounds), 1 obstructed micturition; and 1 neuropathic pain on the obturator territory. Post-operative neuropathic pain was treated by the removal of the mesh. Postoperative hematomas were taken care by drainage by coelioscopy or laparotomy. 

From 48 hours to 2 months after the initial intervention, there were 38 complications in the retropubic group and 8 in the transobturator group. In the retropubic group, we observed 32 obstructed micturitions, 3 vaginal exposure et 3 mesh infections. Mesh infections were treated by removal of the mesh. In the transobturator group, 6 women had obstructed micturition, a woman needed a laparotomy due to infected haematoma of Retzius space and one woman needed to return to the operative room to evacuate a suburethral thrombus that had resulted in obstructed micturition. 

From 2 months to 12 months after initial intervention, there were 31 complications in the retropubic group: 23 mesh exposure (20 vaginal exposure, 2 urethral exposure, 1 non described exposure), 5 obstructed micturitions et 3 chronic pain (among one patient with pain during sexual intercourse).
During this period, there was 6 complications in the transobturator group: 2 obstructed micturitions et 4 vaginal exposure. For the 3 women requiring reintervention for chronic pain, the mesh was removed in 2 cases (by vaginal route or laparotomy). The women presenting pain during sexual intercourse benefited of vaginal trimming without resection of the mesh. 

Beyond 12 months after initial intervention, there was 6 complications in the retropubic group: 3 obstructed micturitions and 3 chronic pain. Women with chronic pain benefited of the removal of the sling by vaginal route or laparotomy or of vaginal trimming without resection of the mesh. 
 During this period, 5 women in the transobturator group had complications: 1 vaginal exposure, 1 urethral exposure, 2 obstructed micturitions and one women with a painful vaginal polyp removed surgically by vaginal route. 

In both groups during the study period, obstructed micturitions were treated either by loosening of the sling vaginally when diagnosed early after surgery (41 women), section of the sling (11 women) or removal of the sling (12 women). Mesh exposure were treated either by vaginal trimming without resection of the mesh (3 patients) or by removal of the mesh (28 patients).

The survival curve without serious complication showed a significant difference between MUS types in favor of the retropubic route (Logrank-p value=0.001 and Figure 1). The estimated incidence at 36 months of serious complications was 5.9% in case of retropubic sling, and 2.8% in the case of a transobturator sling. Taking into account potential confounders, the risk of complication was more than two time lower in the transobturator approach (HR=0.43; IC95%=0.31 to 0.59).This difference remain significant after exclusion of patient with previous history of SUI.
The risk of reoperation for recurrence of SUI was similar between groups (HR=0.97; IC95%=0.58 to 1.69 and Figure 2).

The retropubic route was associated with a higher risk of complication than the transobturator route. On the other hand, there was no difference in reccurence rate needing reoperation between both approach. These results are in line with a previous clinical trial comparing both approach(2). However, more recent meta-analyses did not confirmed those differences(3). Differences between both groups were related mostly to voiding obstruction. On the other hand, other perioperative events and other medium term events were also more frequent in the retropubic group. Baselines characteristics were different in particular an history of SUI procedure was more frequent in the retropubic group, nonetheless the difference in serious complications rate remains after excluding these women.

Analysis of long term results in our registry show higher risk of serious complication in the surgical treatment of SUI with the retropubic route compared with transobsturator (in-out or out-in) with a similar efficacity. 
However, the design of our study ignore complications requiring medical treatment, including painful symptoms that may impact the quality of life. It now remains to analyze the typology of the complications to explain which would be related to the difference in route.

Fritel X, Campagne-Loiseau S, Cosson M, Ferry P, Saussine C, Lucot J-P, et al. Complications after pelvic floor repair surgery (with and without mesh): short-term incidence after 1873 inclusions in the French VIGI-MESH registry. BJOG Int J Obstet Gynaecol. janv 2020;127(1):88-97
Richter HE, Albo ME, Zyczynski HM, Kenton K, Norton PA, Sirls LT, et al. Retropubic versus transobturator midurethral slings for stress incontinence. N Engl J Med. 3 juin 2010;362(22):2066-76
Leone Roberti Maggiore U, Finazzi Agrò E, Soligo M, Li Marzi V, Digesu A, Serati M. Long-term outcomes of TOT and TVT procedures for the treatment of female stress urinary incontinence: a systematic review and meta-analysis. Int Urogynecology J. août 2017;28(8):1119-30

Continence 2S2 (2022) 100346
DOI: 10.1016/j.cont.2022.100346